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INA301-Q1: Filter size

Yuto Kitamura
Expert 7415 points

Part Number: INA301-Q1
Other Parts Discussed in Thread: INA301

Hi team,

My customer is trying to use INA301 for current sense.

Do you have the recommended values for Rfilter and Cfilter?  (showed in figure 39 in the datasheet)

The other component size is below.

Supply voltage: 20~32V

Rshunt: 10mohm

Rlimit: 46.5kohm (Ilimit: 18.6A)

Rfilter: ??

Cfilter: ??

Best regards,

  • +1
    TI__Expert 7190 points

    Yuto-san,

    Thanks for the question and using the E2E forum.

    The basic answer is that it depends on what cutoff frequency your customer needs. The equation to calculate your Rf and Cf values is 

    Cf = 1 / (2*pi*fc*(2*Rf)) where Cf is the filter capacitor, fc is the cutoff frequency, and Rf is the filter resistor.

    For example, if you needed an fc of 1.6kHz, and selected 100 Ohm resistors, your Cf value would be ~497nF.

    Typically, it is easiest to start by selecting your Rf values, keeping them as low as possible to avoid adding extra input errors, and then calculating your Cf values.

    To help show how these input filter resistors can add unwanted input errors, we have a great video that can walk you through it here.

    Please let us know if you need any additional help.

    Louis